Formation of core-type macroscopic morphologies in Cu-Fe base alloys with liquid miscibility gap

Abstract

The effects of alloying elements on the macroscopic morphologies in Cu-Fe base alloys were experimentally investigated. It was found that macroscopic homogeneity can be achieved by the addition of Mn, Ni, Al, or Co in the Cu-Fe base alloys, while the core-type macroscopic morphologies with Cu-rich or Fe-rich cores, which are radially separated as two layers in the inner and outer parts of the ingot solidified in the cast-iron mold, were formed by the addition of C, Cr, Mo, Nb, Si, or V. It is shown that the formation of the core-type macroscopic morphology is strongly connected with the existence of a stable miscibility gap of the liquid phase in the Cu-Fe base alloy due to the addition of alloying elements. The liquid phase with less volume fraction always forms the center part. This result can be explained by a mechanism that the minor droplets as the second phase are forced to move into the thermal center due to Marangoni motion, which is caused by the temperature dependence of interfacial energy between two liquid phases.

Microstructural Evolution of Alloy Powder for Electronic Materials with Liquid Miscibility Gap

“…Since this finding, extensive work has been carried out on the mechanism [5][6][7] of the formation of this egg-type microstructure, the role of interfacial energy, 8 and bulk ingots with a core-type microstructure. 9 Very recently, we performed phase field simulation of the microstructural evolution of immiscible liquid powder, 10 which permits the general treatment of composite powder with a core/shell structure. It is noted that an egg-type microstructure is obtained in epoxy resin, where a similar effect of interfacial tension gradient occurs.…”

Experimental Investigation and Thermodynamic Reassessment of the Cu-Fe-Si System

“…On the basis of the extensive experimental work on Cu-Fe-based alloys from Wang et al, [3,57] the following two conclusions can be drawn: (1) the minor volume phase always occupies the core part, that is, the Fe and Cu core structures are observed in the Cu-and Fe-rich alloys, respectively; and (2) the core macroscopic morphology can be obtained if the volume fraction difference of the two liquid phases is larger than~10 pct at the monotectic temperature. Figure 12(a) shows the calculated vertical section along 3 wt pct Si, according to the present thermodynamic parameters.…”

Liquid Phase Separation Mechanism of Cu‐40 wt.% Pb Hypermonotectic Alloys

“…e globules of minority liquid phase were generated, and then they grew and migrated under a combined effect due to complex factors, including the Marangoni motion [8], Brownian motion [9], convective flow [10], gravity [11], wettability between the two liquid phases [12], and cooling rate [13]. Apparently, the seriously segregated microstructure of immiscible liquid alloys under normal ground conditions has greatly restricted their broad applications.…”